1. Field of the Invention
The present invention relates to a wireless power receiving device and a wireless power transmission device.
2. Description of the Related Art
A wireless power transmission technology has been drawing attention in which power for charging a power storage device mounted in an electric vehicle or the like is supplied wirelessly from outside the vehicle without using a power cable.
In such a wireless power transmission technology, the occurrence of an abnormal condition in a device involved during transfer of high power may lead to degradation of or damage to the device mounted in the electric vehicle. Accordingly, there has been an increasing demand for the improvement of the safety of the entire device that uses a wireless power transmission technology.
In response to such a demand, Japanese Unexamined Patent Application Publication No. 2013-5615 proposes a power receiving device that includes a discharge unit for discharging reception power received by a power receiving unit in the case of occurrence of an abnormal condition in the power receiving device. Specifically, the power receiving device described in Japanese Unexamined Patent Application Publication No. 2013-5615 includes the discharge unit that has a relay and a resistor, which are connected to each other in series, and that is connected between paired power lines connecting a rectifier and a power storage device. In the case where an abnormal condition occurs in the power storage device and it is not possible to perform charging of the power storage device, power that remains is consumed by the resistor after power transmission is stopped so as not to be fed to the power storage device to thereby appropriately protect the power receiving device.
With the technology disclosed in Japanese Unexamined Patent Application Publication No. 2013-5615, in the case where an abnormal condition occurs in the power storage device and it is not possible to perform charging of the power storage device, power that remains is consumed by the resistor after power transmission is stopped. Accordingly, in the case where an abnormal condition, such as an overvoltage, in the power receiving device continues until power transmission is stopped, a voltage applied to the power receiving device may keep rising. However, the technology disclosed in Japanese Unexamined Patent Application Publication No. 2013-5615 does not take into consideration such a voltage rise when an abnormal condition of the power receiving device continues. In the case where a voltage applied to the power receiving device rises and exceeds an allowable level of power consumable by the discharge unit, a protective circuit element itself, which forms the discharge unit and is to provide a protective function, is damaged, which has been an issue.
In the case where an abnormal condition, such as an overvoltage, in the power receiving device continues until power transmission is stopped and a voltage applied to the power receiving device keeps rising, a voltage applied to a device to be protected also rises, which may result in degradation of or damage to the device. As a result, a stable protective function may be impaired, which has also been an issue.